Disk recording medium for embodying high capacity hard disk drive

ABSTRACT

A disk recording medium includes a servo track pattern where a gray code field has been deleted, capable of embodying a high capacity hard disk drive. The hard disk drive which uses as a recording medium, a disk having a plurality of servo sectors for each track, includes: a first plurality of servo track patterns on each track, the number of first servo track patterns equal to the total number of first servo sectors existing on each track divided by the number of heads of the hard disk drive, each of the plurality of servo track patterns having a gray code field for providing information for each track; and a second plurality of servo track patterns on each track, the number of second servo track patterns equal to the total number of servo sectors existing on each track minus the number of first servo track patterns, each of the second plurality of servo track patterns corresponding to the first servo track pattern but with the gray code field deleted.

CLAIM OF PRIORITY

This application make reference to and claims all benefits accruingunder 35 U.S.C §119 from an application entitled DISK RECORDING MEDIUMFOR EMBODYING HIGH CAPACITY HARD DISK DRIVE AND SERVO CONTROL METHODPERFORMED THEREBY earlier filed in the Korean Industrial Property Officeon Aug. 28, 1995 and assigned Korean Application No. 26969/1995.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a servo control in a hard disk drive(hereinafter, referred to as an HDD) and, in particular, to a diskrecording medium comprising a plurality of servo track patterns in orderto embody a high capacity hard disk drive and a servo control methodperformed thereby.

2. Description of the Related Art

Conventionally, an HDD which is widely used as an auxiliary memory of acomputer system, is generally constructed with a read/write channel forreading data stored on a disk and for converting the read data, i.e.,converting an analog signal into a digital signal, a microprocessor forcommunicating with a host computer and for performing an overall controloperation of the HDD system, and a servo controller for moving a head toa specific position on the disk. Using a servo control, the HDDconstructed as described above operates in a track seek mode and a trackfollowing mode, in accordance with a moving distance of an actuator. Thetrack seek mode moves the actuator to a target track and the trackfollowing mode controls the head of the actuator while placed on thetarget track, so that the head lies on-track. In the conventional HDD, avelocity control of the actuator is effected in the track seek mode, anda position control is effected in the track following mode. The diskused as a recording medium of the HDD is divided into a number of trackswhere a servo sector and a data sector are alternately arranged suchthat about 9˜10% of the entire capacity of the disk is utilized as theservo sector.

Typically, the track for each head on a platter and a hard disk driveusing a multiple platter arrangement includes a data sector having a IDfield and a data field and a servo sector consisting of preamble, aservo address mark, a gray code field for providing the information foreach track number and a plurality of servo bursts for providing positionerror signals required for operation of the track seek mode and thetrack following mode. Lastly, a PAD field is provided to give atransition margin from the servo sector to the data sector.

The patents to Hetzler, U.S. Pat. No. 5,523,903, BANDED MAGNETICRECORDING DISK WITH EQUALLY-ANGULARLY-SPACED SERVO SECTOR, Hetzler, etal., U.S. Pat. No. 5,526,211, SECTOR ARCHITECTURE FOR FIXED BLOCK DISKDRIVE, Machado, et al., U.S. Pat. No. 5,418,657, TRACK ADDRESS DETECTINGMEANS BY HDD SECTOR SERVO METHOD, and Chiao, et al., U.S. Pat. No.5,515,212, VERY-HIGH DENSITY DISKETTE FORMAT METHOD AND COMPUTERIMPLEMENTED PROCESS, each discloses prior art disk drive arrangementshaving formats similar to those noted above.

None of the cited art has been able to reduce the size of the servosector by eliminating the gray code field from some of the servo sectorsin each track as in the present invention so as to increase the densityon the hard disk drive as in the present application.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a diskrecording medium including a servo track pattern where a gray code fieldhas been deleted, capable of embodying a high capacity HDD.

It is another object of the present invention to provide a servo controlmethod of a HDD which uses as a disk recording medium, a disk having aservo track pattern where a gray code field has been deleted, capable ofembodying a high capacity HDD.

These and other objects can be achieved according to the presentinvention with a servo control method of an HDD comprising: providing adisk having a plurality of first servo track patterns including a graycode field for providing track information for each track, and aplurality of second servo track patterns which fail to include the graycode field of the first servo track patterns, both the first and secondtrack patterns being positioned on the same track; providing a head forreading the data from a given track of the disk or writing the data onthe given track; checking, in response to a data read/write commandreceived from a host computer, whether or not the head must move to atarget track; if it has been determined that the head must move to thetarget track, repeatedly switching a head number following the headswitched at present, in a sequential manner, thereby performing a trackseek; after performing the track seek, checking whether or not avelocity of the head is decreasing; if it has been determined that thevelocity of the head was decreasing, fixing the head on the diskincluding the target track, thus performing the track following.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of this invention, and many of theattendant advantages thereof, will be readily apparent as the samebecomes better understood by reference to the following detaileddescription when considered in conjunction with the accompanyingdrawings, in which like reference symbols indicate the same or similarelements components, wherein:

FIG. 1 illustrates sector formats for each head wherein a servo sectorand a data sector are alternately arranged;

FIG. 2 illustrates a servo track pattern written in the servo sector ofFIG. 1;

FIG. 3 illustrates a servo track pattern according to an embodiment ofthe present invention;

FIG. 4 illustrates sector formats for each head according to anembodiment of the present invention;

FIG. 5 is a flowchart illustrating the servo control of a servocontroller according to an embodiment of the present invention; and

FIG. 6 illustrates a general velocity variation characteristic of thehead in a track seek mode and a track following mode.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Throughout the drawings, it is noted that the same reference numerals ofletter will be used to designate like or equivalent elements having thesame function. Further, in the following description, numerous specificdetails are set forth to provide a more thorough understanding of thepresent invention. It will be apparent, however, to one skilled in theart that the present invention may be practiced without these specificdetails. A detailed description of known functions and constructionsunnecessarily obscuring the subject matter of the present invention hasbeen omitted in the following description for clarity.

FIG. 1 shows the sector formats for given tracks on platters incorrespondence with each head (headφ, head 1, head 2, and head 3) in theHDD using a multiple platter system. As shown in FIG. 1, a servo trackpattern written for each servo sector is written with a bank writingmode or with a parallel writing mode. The data sector of FIG. 1 istypically divided into an ID (identification) field and a data field.Header information for identification of the corresponding data sectoris written in the ID field, and the digital data is written in the datafield. The servo track pattern of FIG. 1 is written in the servo sectorpositioned before and after the data sector as illustrated in FIG. 2.

With reference to FIG. 2, the servo sector includes a preamble, a servoaddress mark (hereinafter, referred to as a SAM), a gray code field,servo bursts (A, B, C and D) and a PAD field. Upon reading the servoinformation, the preamble provides a clock synchronization and alsoprovides a gap before the servo sector. The SAM indicates the start ofthe servo control and to read the gray code field following the SAM.That is, the SAM provides a reference point for generating all kinds oftiming pulses related to the servo control. Further, the gray code fieldprovides the information for each track number and the servo bursts(A,B,C and D) provide position error signals (hereinafter, referred toas PES) required for operation in the track seek mode and the trackfollowing mode. The PAD field is to provide a transition margin from theservo sector to the data sector. As an example, a servo controltechnique for a HDD comprised of a disk having 72 servo sectors pertrack where the servo track patterns are written and a spindle motor forrotating the disk at a constant speed of 4500 RPM, is described below.

Once a data read/write command is received from an external device(e.g., the host computer), the microprocessor checks whether or not atrack seek must be performed. When it has been determined that a trackseek must be performed, the microprocessor switches to the track seekmode, to perform the track seek mode. The head located at the surface ofthe disk including the target track, is selected by a head switchingoperation. After controlling the head to lie on-track of the targettrack using the servo information which is sensed at every sampling viathe selected head by the head switching operation, the microprocessorperforms the read/write operation. In this case, each PES for all of the72 servo sectors is required for sampling every servo sector. Since thegray code field always exists in usual servo track patterns, the graycode field is recorded and a sampling value read whenever the servosampling is performed. As a consequence, the number or the length of theservo sectors in the high capacity HDD cannot be reduced.

With regard to FIG. 3, the servo track pattern according to a embodimentof the present invention, is comprised of a first servo track patternSTPφ wherein track information for each track is written and a secondservo track pattern STP 1 where a gray code field corresponding to thefirst servo track pattern STPφ has been deleted. With reference to FIG.3, the first servo track pattern STP φ has the same construction as theservo track pattern as illustrated in FIG. 2, except that the positionsof the gray code field and the servo burst (A,B,C and D) are reversed.The second servo track pattern STP 1 has the same construction as thefirst servo track pattern STPφ but the gray code field has been deleted.The PADφ field is the minimum timing margin required to generate thetiming pulse for reading the servo burst signal, and the PAD1 field isthe transition margin from the servo sector to the data sector.

FIG. 4 illustrates sector formats for each head according to anembodiment of the present invention, wherein the first and second servotrack patterns STPφ and STP 1 are conventionally written on the disk. Anexplanation of the steps of setting the number of first and second servotrack patterns STPφ and STP 1 which are written on the surface of eachtrack is provided below.

Assuming that two disks are used as the disk recording medium of the HDDaccording to an embodiment of the present invention and assuming thateach track arranged concentrically on the disk has 72 servo sectors, thenumber of first servo track patterns STPφ is made equal to the totalnumber of servo sectors existing on the each track divided by the numberof heads. The number of second servo track patterns STP 1 is made equalto the total number of servo sectors existing on each track minus thenumber of first servo track patterns STPφ. In the embodiment of thepresent invention, 18, (that is 72/4) first servo track patterns STPφand 54 (that is 72-18) second servo track patterns STPφ are written onthe servo sector of each track. The servo sector where the first servotrack patterns STPφ and the second servo track patterns STP 1 arewritten, can be set with a consequential method embodied as anembodiment of the present invention.

Primarily, the number of servo sectors existing on each track is dividedby the number of heads. If the first servo track pattern STPφ is writtenin the servo sector wherein the head number is the same as the remainderafter division by the number of heads, and the second servo trackpattern STP 1 is written in the remaining servo patterns except for theabove servo sector, the servo sector on the given track whichcorresponds to each head (headφ, head 1, head 2 and head 3) has theservo track pattern as shown in FIG. 4.

As can be seen from FIG. 5, illustrating the servo control of the HDDwhich uses as a recording medium, the disk having the servo trackpatterns STPφ and STP 1, the microprocessor checks, in step 10, whetheror not the read/write command has been received from an external device,such as the host computer. If it has been determined that the read/writecommand has not been received, the microprocessor continues the stand-bymode state. However, if it has been determined that the read/writecommand has been received, the microprocessor proceeds to step 12, andchecks whether or not the head must move to the target track. That is,the microprocessor checks whether or not the track seek must beperformed. If it has been determined that the track seek must beperformed, the microprocessor proceeds to step 14, thereby successivelyswitching from one head to a following head, thereby to performing thetrack seek. The steps of reading each track number by the head switchingoperation is more concretely explained as follows.

As depicted in FIG. 4, it is assumed that the present head number isindicated as the headφ and the head 4 is positioned at the position oftrack numberφ. In this case, when the command to read/write the data atthe given sector of the track number N exists at the surface of the diskcorresponding to head 3, the microprocessor performs the head switchingoperation in a sequential manner such as headφ (track number 1)→head 1(track number 1)→head 2 (track number 2)→head 3 (track number 3)→headφ(track number 4), thereby reading the corresponding track number fromthe first servo track pattern STOφ and thus, recognizing the positioninformation of the head 4. Upon the track seek, the microprocessorchecks with a seek table to determine whether or not the head is beingdecelerated. If the head is being decelerated, the microprocessorproceeds to step 18 through step 20. That is, the track following modeis entered and track following is performed according to head switchingand then the head is fixed. In other words, the microprocessor fixes thehead in correspondence with the target track after reading the servoinformation from the first and second servo track patterns STPφ and STP1 written on the target track by performing the track following mode, sothat the servo sampling can be performed. After that, in step 22, themicroprocessor performs the data read/write operation on the data sectorof the target track, thereby finally completing the servo controlaccording to the embodiment of the present invention.

The velocity variation characteristic of the head of the HDD upon thetrack seek or the track following, can be seen as shown in FIG. 6.Namely, as depicted in FIG. 6, in the conventional head disk drive, themoving velocity of the head is increased in an interval betweenpositions X0 and X1 of the track, is constant in an interval betweenpositions X1 and X2 of the track, and is decreased in an intervalbetween positions X3 and X4 thereof.

As may be apparent from the foregoing, the present invention hasadvantages in that the high capacity hard disk drive can be embodied bywriting on the disk, two servo track patterns, i.e., a servo trackpattern having a gray code field and a servo track pattern having nogray code field, thereby reducing the length of the servo sector. Aswell, upon the track seek, since the head switching operation and thehead moving operation are performed at the same time, the offset foreach head as well as the performance of the servo control can beimproved advantageously.

While there have been illustrated and described what are considered tobe preferred embodiments of the present invention, it will be understoodby those skilled in the art that various changes and modifications maybe made, and equivalents may be substituted for elements thereof withoutdeparting from the true scope of the present invention. In addition,many modifications may be made to adapt a particular situation to theteaching of the present invention without departing from the centralscope thereof. Therefore, it is intended that the present invention notbe limited to the particular embodiment disclosed as the best modecontemplated for carrying out the present invention, but that thepresent invention includes all embodiments falling within the scope ofthe appended claims.

What is claimed is:
 1. A disk for a hard disk drive which uses as arecording medium, the disk having a plurality of servo sectors for eachtrack, the disk comprising:a first plurality of servo track patterns oneach track, the number of first servo track patterns equal to the totalnumber of servo sectors existing on each track divided by the number ofheads of the hard disk drive, each of said first plurality of servotrack patterns having a gray code field for providing information foreach track; and a second plurality of servo track patterns on eachtrack, the number of second servo track patterns equal to the totalnumber of servo sectors existing on each track minus the number of saidfirst servo track patterns, each of said second plurality of servo trackpatterns corresponding to said first servo track patterns with said graycode field being deleted.
 2. The disk as defined in claim 1, whereineach of said first servo track patterns is comprised of:a preamble forproviding a clock synchronization upon reading servo information; aservo address mark for providing a reference point for generating timingpulses related to a servo control; a first PAD field, for providing atransaction margin upon reading said servo information; servo bursts forproviding positional error signals of said head; a gray code field forproviding track information for each track; and a second PAD field forproviding said transaction margin upon reading said servo information;wherein said preamble, said servo address mark, said first PAD field,said servo bursts, said gray code field, and said second PAD field arewritten on said first servo track patterns in a sequential manner. 3.The disk as defined in claim 2, wherein said the first servo trackpatterns are written on a number of said servo sectors equal to thetotal number of servo sectors existing on each track divided by thenumber of heads of the hard disk drive, and wherein said second servotrack patterns are written on all other servo sectors.